Re: Hot Backups

In article <D78GMr.1yL_at_lanier.com>, Don Vick <dvick_at_lanier.com> wrote:
>When a tablespace is in backup status, Oracle saves all
>update activity in the redo logs and catches up the data files after the
>backup is done. Redo logs cannot be archived if they contain active data,
>so you run the risk of running out of online redo logs and stalling your
>system (i.e., blocking udpates). (I may have some details wrong here, but
>that is the general idea. :-)

Not true. The system starts logging more information than usual but it doesn't have to keep it online. Changes are written to the datafiles just as if the system was not being backed up. The backups of this data is inconsistant therefor the offline archive files are needed to roll the datafile forward to a consistant state. But the disk version was never effected. With the exception of checkpoints not being written to the datafile headers. (O7 Concepts 24-4)

I read once (but cant find the reference now) that one thing that is different during a Hot Backup is that the entries written to the on line log files are larger than usual. Basically instead of writing block offset references of changed data V7 must write the entire changed block.

Can anyone confirm that this is a) still true for 7.1.3 and b) was ever true?

-- 
Regards, 

Lee E. Parsons                  		
Systems Oracle DBA	 			lparsons_at_world.std.com